Abstract

The top-down suppression of pest insects by their natural enemies, such as insectivorous bats, represents an important ecosystem service in agricultural systems. Recognizing the importance of bats to suppress pest populations and further conserve their populations near agricultural systems could reduce damage to crops thereby potentially increasing the monetary gain of farmers. Viticulture represents one of the most extensive and economically important agricultural crops in the Mediterranean biome. While pest consumption by bats has been recently revealed in vineyards, direct evidence of the reduction of grapevine pests by bats in vineyards is lacking, and their benefits to winegrape production remains to be quantified. Using large nocturnal exclosures in vineyards, we examined the top-down effects of aerial insectivorous bats in suppressing insect populations by assessing leaf and grape cluster damage; we also examined the benefit of these natural pest predators by quantifying resulting increases in potential vineyard yield. Grapevine plants excluded from bats had significantly higher leaf herbivory and greater grape cluster damage than control plots. Grape cluster damage was 7% lower on control plots, yielding an average economic benefit of US$188-$248/ha/year due to bat predation. These results provide the first experimental evidence that bats reduce grapevine pest insect infections and thus increase vineyard yield and winegrowers' income. Therefore, bats should be included in future biodiversity conservation plans in vineyards and be considered within agricultural management strategies based on natural pest suppression.